The energy demand increases dramatically with the fast economic development in China. At present, China has become the largest energy-importing country in the world. Furthermore, environmental problems accompanied with consumption of the ore-based energy, such as fog and haze, are increasingly rapidly. Therefore, it is urgent to exploit the clean and sustainable energy. As a renewable and clean energy source, the development and utilization of solar energy is one of the hotspots in the field of energy study.
As an important type of solar cells, the dye-sensitized solar cell has been widely concerned all over the world. In 1991, the research group of Grätzel produced a device by adsorbing RuL2(μ-(CN)Ru(CN)L′2)2 (L=2,2′-bipyridyl-4,4′-dicarboxylic acid, L′=2,2′-bipyridyl), a trinuclear ruthenium dye reported by Amadelli et al as a sensitizer, on a high quality TiO2 nanocrystalline film and a power conversion efficiency of 7.1% was achieved under the simulated sunlight. Therefrom, the widely research of dye-sensitized solar cell was basking in a great boom.
Dye-sensitized solar cells have lower manufacturing cost, variety of colors and good appearance compared with traditional inorganic semiconductor solar cells. Furthermore, flexible dye-sensitized solar cells are featured with their lightweight, foldable and windable abilities, and thus can be broadly used in daily life.
At present, all of the commercial available dyes are complexes containing a noble metal ruthenium. Due to its rare resource, Ruthenium-based materials are very expensive, which greatly limits the production and application thereof in large scale. Meanwhile, as another promising materials, the pure organic dyes is in full flourish despite the fact only a few devices made from pure organic dye can achieve a power conversion efficiency over 10% currently. Furthermore, the inconvenient synthesis of most of the materials used in high efficient devices also hinders the development of the pure organic dyes in dye-sensitized solar cells.